First, a system is known to provide a lighting system to illuminate a room using an optical fiber. An example of such a system is the GE Light Engine.TM.. Second, a system is known to use optical fiber to provide data. Typically these two are provided through two different optical systems. Is it possible to do both with one system?
It has been proposed to data-modulate a visible light from a lamp used for illumination. This proposal has been difficult to implement because large voltages and currents are required. Further, data rates in the proposed system are inherently limited to rates below several hundred kilobits per second because excited states in the lamps of the proposed system have long life times. In addition, shot noise is a problem associated with data-modulation of illuminating lamps because of the enormous optical power levels involved. In general, light sources that include both visible and infrared spectra create noise problems for data communication equipment that rely on infrared light sources for data transmission.
In fiber distributed lighting systems, it would be desirable to use a light fiber to distribute data as well as light for illumination.
There are two types of wireless communication: radio frequencies (RF) and light (often infrared (IR) but it could be visible light which is far less common). There are many reasons why visible wireless communication is not found in data communication applications. One reason is that the equipment receiving visible light data signals would also be sensitive to non-data signals such as sunlight and light from desk lamps, fluorescent ceiling bulbs, etc. Further, visible light is not used because the sources of visible light, light bulbs or fluorescent tubes for example, cannot have very fast signals superimposed on them or large modulation depths--because of the physics of how they generate light (thermally, in the case of a typical light bulb).
Current IR wireless standards call for data rates from 2,400 bits per second up to 115,200 bits per second and some products are even faster starting at 1,000,000 bits per second. For these two reasons, it is not practical to use the same light source to illuminate a room and send data at the same time.
According to the invention presented and claimed here, a second light source that is capable of being modulated at higher speeds must be combined with a light source that is being used for visible illumination. There are visible light sources such as red light-emitting diodes (LED) that are not used for room illumination that can be modulated up to 1,000,000 bits per second. Again, the reason that you would not want to use these is that the receiving equipment would have a tough time distinguishing what is signal and what is noise.
This brings us to infrared light sources. For IR, the problem with interfering noise is greatly reduced by using filters to remove the visible light noise before it reaches the data receiving equipment. This receiving equipment will still be sensitive to infrared noise that is present in sunlight, tungsten light bulbs and fluorescent lights.
In rooms with existing light fixtures, this infrared noise is a problem that IR wireless equipment has to live with. It is not practical to expect people to put IR filters on every light in their office or home but, with rooms or offices that install fiber-based light systems such as the GE Light Engine.TM. it is possible and practical to filter out IR noise at the light source before it is distributed for illumination. This means that IR data communications equipment that is used in rooms or offices illuminated by an IR filtered visible light source will not see any noise light sources (except sunlight possibly). This is one advantage to using a fiber based lighting system. The other advantage is that other light sources can be combined with the visible light and get distributed as well. In the invention described and claimed here, an IR data signal gets combined with a visible light source that has its IR filtered out. So, the only things travelling down the light pipes are the visible light and the IR data signal and no IR noise. The bandwidth IR data signal can be whatever the application calls for (up to the limits of the IR source which for LEDs is currently under 50,000,000 bits per second, but for lasers it is much higher). So, the IR data source does not necessarily have to have a bandwidth that is higher than the visible light source is capable of! In practice, though, this will be the case in signals greater than 1,000,000 bits per second.